Health A-Z

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What Is It?

Premenstrual syndrome (PMS) is a collection of symptoms that many women experience during the one to two weeks before a menstrual period. These symptoms may be physical, psychological and emotional. They disappear soon after the start of menstrual bleeding.

Researchers are not certain what causes PMS. The most popular explanation is that PMS symptoms are related to cyclic changes in:

  • Female sex hormones

  • Pituitary hormones

  • Prostaglandins

  • Certain brain chemicals (neurotransmitters)

There is some evidence that magnesium deficiency could play a role.

Lifestyle may play a significant role in PMS. PMS symptoms appear to be most troubling in women who:

  • Smoke

  • Lead stressful lives

  • Rarely exercise

  • Sleep too little

  • Have a diet high in:

    • Caffeine

    • Alcohol

    • Salt

    • Red meat

    • Sugary foods

However, it's not clear whether these factors increase your risk of PMS or if PMS accounts for these differences in lifestyle. For example, it is more likely that PMS causes stress rather than that stress causes PMS.

Medications may exaggerate the symptoms of PMS. Oral contraceptives cause symptoms of PMS in some women. However, in some women, symptoms improve or disappear while using birth control pills.

There is some controversy in the medical community about the difference between premenstrual discomfort and true PMS. Premenstrual discomfort is fairly common among women of childbearing age. It affects about three-quarters of all menstruating women.

However, fewer than one in ten women have symptoms that are severe enough to disrupt their personal relationships or interfere with their work and home responsibilities. Some doctors feel that only women who have such severe symptoms have true PMS.

Other doctors use a less stringent definition for PMS. Their definition includes mild to moderate symptoms.

Severe mood symptoms are sometimes named premenstrual dysphoric disorder (PMDD).

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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